1. Field of the Invention
The invention relates to a method and to a circuit arrangement for separating luminance and chrominance signals of a CVBS signal, in particular a comb filter arrangement for PAL signals.
2. Prior Art
In analog colour television transmission methods, the transmitted CVBS signal comprises luminance and chrominance signals. In the case of PAL and NTSC, the chrominance signal, for its part, is composed of two colour difference signals (U/V signals in the case of PAL, I/Q signals in the case of NTSC) which are modulated in quadrature phase onto a colour subcarrier.
In a television receiver, the luminance and chrominance signals must be separated from one another again in order to permit separate further processing. For this, comb filters are used which carry out a combination of a plurality of adjacent lines on the basis of line, field and frame delays for the purpose of signal separation. It is customary here to work with a picture contents-dependent controller which, depending on how the chrominance signals are structured, switches over between different filter algorithms.
In the case of conventional comb filters which split the CVBS signal into the luminance signal and the chrominance signal, which comprises the two colour difference signals still to be demodulated, the identification of colour edges, in particular, is not always carried out in a manner free from errors. This can lead to incomplete separation of the luminance and chrominance signals, so that it is frequently the case that cross effects cannot fully be avoided.